What is Multi Layer PCB?

A Multi Layer PCB can be defined as a PCB made of two or more foil conductive layers. The biggest difference between Multi Layer PCB and single panel and dual panel is the addition of internal power layer and ground layer. The power supply and ground network are mainly on the power layer. Each substrate layer on a Multi Layer PCB has conductive metal on both sides, uses a special adhesive to hold the boards together, and insulation exists between each board. The layout of Multi Layer PCB is mainly based on the top layer and the bottom layer, supplemented by the middle layer, so the design method of Multi Layer PCB is essentially the same as that of dual panel.

With the continuous development of electronic technology, Multi Layer PCB Manufacturing is developing rapidly towards the direction of high density, high precision and high level digitalization. Technologies such as fine line, narrow aperture penetration and blind hole can meet the market demand. Multi Layer PCB are widely used in the manufacture of electronic products due to their flexible design, stable and reliable electrical performance and excellent economic performance.

Multi Layer PCB Manufacturing has superior assembly density, small size and light weight. Due to the elevated assembly density, it reduces the connection between components, improves the reliability, increases the number of wiring layers and the flexibility of the design, and forms a high-speed transmission circuit with a certain impedance.

Multi Layer PCB high-speed transmission circuit, circuit, magnetic circuit shielding layer, metal core heat dissipation layer can be set to meet the needs of shielding, heat dissipation and other special functions, easy installation, high reliability.

Multi Layer PCB Manufacturing Problems

The solid board can be divided into single layer board, double layer board and Multi Layer PCB Manufacturing. Multi Layer PCB Manufacturing is mainly used in all kinds of electronic equipment with complex structure and large wiring space, such as 5G base station, server, automotive electronics, desktop computers, etc. Therefore, driven by 5G, cloud computing and different energy vehicles, the market demand for Multi Layer PCB Manufacturing has been growing in recent years.  

1. Multi Layer PCB board splicing problem

Multi Layer PCB Manufacturing can be linked in a variety of ways: splice, seam, oblique grinding lap. Quality problems can occur when the links between boards are defective, such as uneven board ends due to improper operation and misalignment between boards.

2. The Multi Layer PCB is too tight or too loose

If the splicing process is used for Multi Layer PCB, there will be a gap between the board and the board, which will cause insufficient nail holding force. If it is too tight, it will cause lamination. Seam joint and oblique grinding lap joint can effectively avoid these quality problems when making Multi Layer PCB.

3. The color or finish of Multi Layer PCB board is inconsistent

If the color or finish of Multi Layer PCB veneer is inconsistent, this is because of improper material selection, did not achieve the "original tree collocation";  when the board is assembled, the front and back of the two boards are inconsistent, and the loose surface and tight surface are reversed. Only to improve the technical level of the operator, more technical training, to strengthen the sense of responsibility of the operator.

4. Multi Layer PCB board missing edge, board embryo edge is not uniform

If the length of the core board of Multi Layer PCB is insufficient and the alignment principle is not followed during operation, the edge of the board will be damaged. Only when purchasing, strictly control the length of the core board and the size of the table board, strengthen production management, improve the skills and responsibility of the operator, and try to use skilled workers.

Multi Layer PCB quality assessment parameters

A qualified Multi Layer PCB has strict requirements for the quality of PCBA processing. What are the common parameters related to the quality assessment of Multi Layer PCB? The commonly used parameters for evaluating the quality of Multi Layer PCB are:

Glass transition temperature (Tg value)

Coefficient of thermal expansion (CTE)

PCB decomposition temperature (Td)

Heat resistance

Electrical performance

Water absorption of PCB

HDI multi layer pcb common laminated structure

Laminated structure is an influential factor affecting the EMC performance of PCB board, and also an essential means to suppress electromagnetic interference. With the emergence of high-speed circuits, the complexity of PCB board is getting higher and higher. In order to avoid the interference of electrical factors, the signal layer and the power layer must be separated, thus HDI multi layer PCB design is involved. So, what are the common HDI multi layer PCB?

1. A simple laminated printed board

The layer is 6 layers at a time, and the laminated structure is (1+4+1). This kind of plate is the most simple, that is, there is no buried hole in the inner layer, a pressing is completed. Different from HDI multi layer pcb, it requires multiple processes such as laser drilling blind holes.

2. Conventional HDI Multi Layer PCB

Primary lamination HDI 6 layers, laminated structure is (1+4+1), the structure of this kind of board is (1+N+1), (N≥2, N even), this structure is the current industry's mainstream design of primary lamination board, multi layer PCB embedded holes, need to complete the secondary pressing.

3. HDI multi layer PCB of conventional secondary stacking

Secondary layer HDI 8 layers, stacked into a structure of (1++1+4+1+1). The structure of this kind of plate is (1+1+N+1+1), (N≥2, N even). This structure is the mainstream design of secondary stacking in the industry at present. The embedded multi layer PCB has buried holes and needs three times pressing to complete.

4. HDI multi layer PCB of the second conventional secondary stacking

Secondary layer HDI 8 laminate, laminated structure is (1+1+4+1+1). The structure of this kind of plate (1+1+N+1+1), (N≥2,N even), although it is the structure of secondary laminated board, but the location of the buried hole is not between (3-6) layers, but between (2-7) layers, such a design can reduce the pressing once, so that the HDI plate of secondary laminated layer needs three times pressing process, which is optimized to two times pressing process.

5. HDI multi layer PCB with blind hole overlapping design

Buried holes (2-7) layer is stacked above the blind hole, secondary layer HDI 8 layers, stacked structure is (1+1+4+1+1). The structure of this type of plate is (1+1+N+1+1 +1), (N≥2, N even), the internal multilayer plate has a buried hole, need to complete the secondary pressing.

6. HDI multi layer PCB with cross-layer blind hole design

Secondary layer HDI 8 laminate, laminated structure is (1+1+4+1+1). The structure of this kind of plate is (1+1+N+1+1), (N≥2, N even). This structure is a secondary laminated plate with certain difficulty in the production of the industry at present. The internal multilayer plate has holes in the (3-6) layer, which needs three times of pressing.

7. Optimization of HDI multi layer pcb of additional laminated structures

The same can be done for triply laminated printed boards or PCB boards with more than triply laminated. Complete triply laminated HDI boards require four compressions.

Multi layer pcb Manufacturing Process

The drilling process is one of the most crucial processes in multi layer pcb manufacturing process and most PCB manufacturers use CNC drilling machines to drill holes. The location of the positioning holes will be used as data for the drilling procedure, and all plates to be drilled are arranged according to these pins.

In the multi layer pcb manufacturing process, the drilling process needs to be carefully controlled to ensure the quality of the final hole electroplating. The quality of the hole can be controlled by the material properties obtained during the drilling process and the adjustment of the drilling speed and feed rate. If the bit is left in the hole for too long, it will stain the resin;  overly swift a feed rate can also lead to drill bit breakage or rough hole walls. Hole pretreatment and metallization are also vital factors in the production of multi layer pcb Manufacturing with through-hole plating.

Get Multi Layer PCB Manufacturing Process

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